Commit-ID: 0837e3242c73566fc1c0196b4ec61779c25ffc93
Gitweb: http://git.kernel.org/tip/0837e3242c73566fc1c0196b4ec61779c25ffc93
Author: Anton Blanchard <anton@xxxxxxxxx>
AuthorDate: Wed, 9 Mar 2011 14:38:42 +1100
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 16 Mar 2011 14:04:13 +0100
perf, powerpc: Handle events that raise an exception without overflowing
Events on POWER7 can roll back if a speculative event doesn't
eventually complete. Unfortunately in some rare cases they will
raise a performance monitor exception. We need to catch this to
ensure we reset the PMC. In all cases the PMC will be 256 or less
cycles from overflow.
Signed-off-by: Anton Blanchard <anton@xxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: <stable@xxxxxxxxxx> # as far back as it applies cleanly
LKML-Reference: <20110309143842.6c22845e@kryten>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
arch/powerpc/include/asm/reg.h | 1 +
arch/powerpc/kernel/perf_event.c | 24 +++++++++++++++++++++++-
2 files changed, 24 insertions(+), 1 deletions(-)
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 125fc1a..7626fa7 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -880,6 +880,7 @@
#define PV_970 0x0039
#define PV_POWER5 0x003A
#define PV_POWER5p 0x003B
+#define PV_POWER7 0x003F
#define PV_970FX 0x003C
#define PV_630 0x0040
#define PV_630p 0x0041
diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c
index ab6f6be..97e0ae4 100644
--- a/arch/powerpc/kernel/perf_event.c
+++ b/arch/powerpc/kernel/perf_event.c
@@ -1269,6 +1269,28 @@ unsigned long perf_instruction_pointer(struct pt_regs *regs)
return ip;
}
+static bool pmc_overflow(unsigned long val)
+{
+ if ((int)val < 0)
+ return true;
+
+ /*
+ * Events on POWER7 can roll back if a speculative event doesn't
+ * eventually complete. Unfortunately in some rare cases they will
+ * raise a performance monitor exception. We need to catch this to
+ * ensure we reset the PMC. In all cases the PMC will be 256 or less
+ * cycles from overflow.
+ *
+ * We only do this if the first pass fails to find any overflowing
+ * PMCs because a user might set a period of less than 256 and we
+ * don't want to mistakenly reset them.
+ */
+ if (__is_processor(PV_POWER7) && ((0x80000000 - val) <= 256))
+ return true;
+
+ return false;
+}
+
/*
* Performance monitor interrupt stuff
*/
@@ -1316,7 +1338,7 @@ static void perf_event_interrupt(struct pt_regs *regs)
if (is_limited_pmc(i + 1))
continue;
val = read_pmc(i + 1);
- if ((int)val < 0)
+ if (pmc_overflow(val))
write_pmc(i + 1, 0);
}
}
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